Electrolytic zinc

By far, the largest appHcation of zinc powder is for solution purification in electrolytic zinc plants. This appHcation consumed an estimated 17,700 t of powder in 1980. Zinc powder is also used in primary batteries, frictional materials, spray metallizing, mechanical plating, and chemical formulations. 

V. Ramachandran and co-workers, MLMRCOV Corpus Christi Electrolytic Zinc Plant, Hydrometallurgy Symposium, AIME, Adanta, Ga., 1983, p. 982. R. Capps and co-workers. Zinc Eead Kesidue Treatment and Solution Purification at the National Zinc Company, AIME, BardesviUe, OHa., 1984, paper A84-30. 

Galvanic or impressed current anodes are used to protect these components. The anode material is determined by the electrolyte zinc and aluminum for seawater, magnesium for freshwater circuits. Platinized titanium is used for the anode material in impressed current protection. Potential-regulating systems working independently of each other should be used for the inlet and outlet feeds of heat exchangers on account of the different temperature behavior. The protection current densities depend on the material and the medium. 

The excellent resistance of zinc to corrosion under natural conditions is largely responsible for the many and varied applications of the metal. In fact nearly half the world consumption of zinc is in the form of coatings for the prevention of corrosion of steel fabrications exposed to the atmosphere and to water. For its varied applications zinc is obtainable in a number of grades. Ordinary commercial (G.O.B.) zinc contains up to about I -5% total of lead, cadmium and iron. Electrolytic zinc has a minimum zinc content of 99-95% and contains small amounts of the same impurities. Special high-purity zinc has a minimum of 99-99% zinc. Even purer zincs are commercially available. 

When they are additionally connected by an electronically conducting external circnit, the OCV causes electrons to flow through it from the negative to the positive electrode. This is equivalent to an electric current I. This current is the result of reactions occurring at the snrfaces of the electrodes immersed into the electrolyte zinc being oxidized at the negative electrode. 

Electrolytic zinc smelters contain up to several hundred cells. A portion of the electrical energy is converted into heat, which increases the temperature of the electrolyte. Electrolytic cells operate at temperature ranges from 30 to 35°C (86 to 95°F) at atmospheric pressure. During electrowinning a portion of the electrolyte passes through cooling towers to decrease its temperature and to evaporate the water it collects during the process. 

Peacey, J. G. Hancock, P. J. Review of pyrometallurgical processes for treating iron residues from electrolytic zinc plants. Iron Control and Disposal, Proceedings of the International Symposium on Iron Control in Hydrometallurgy, 2nd, Ottawa, Oct. 20-23, 1996, 17-35. 

Goethite A process for removing iron from leach liquors from hydrometallurgical leaching operations. Used in recovering zinc from the residues of the electrolytic zinc process. See also Jarosite, Haematite. 

Jarosite [Named after the mineral, first recognized at Jarosa, Spain] A process for removing iron from the leach liquors from hydrometallurgical operations. First used in 1964 in processing zinc sulfate liquors at Asturiana de Zinc, Spain. Also used for recovering zinc from the residues from the electrolytic zinc process. See also Goethite, Haematite. 

Canadian Electrolytic Zinc, Ltd., 26 564 Canadian Environmental Protection Act (CEPA), 13 542 23 120-121 Canadian nuclear power program, 17 585 Cancer. See also Breast cancer ... 

Electrolytic zinc plants, 12 555 Electrolytic zinc process, 26 565-566 Electrolyzers, industrial, 18 281 Electromagnetic applications, for bulk materials, 23 865-870 Electromagnetic assisted material processing, 23 856-857 Electromagnetic brush (EMB) technology, 7 59... 

Lundin, H. Electrolytic zinc. The determination of small amounts of... 

First, when 1,1-dihaloalkanes are reduced with low-valent titanium derived from TiCU and zinc, it is necessary to add a catalytic amount of PbCU (or Pb) for reproducibility (Equations (5) and (6)). Two kinds of zinc powder are available for laboratory use electrolytic zinc derived by hydrometallurgy and distilled zinc derived by pyrometallurgy. 

The electrolytic zinc is pure and free from lead in contrast, the distilled zinc contains a catalytic amount of lead based 29,30... 

ZnBr2 can also be partially reduced (—1.4 < E < — 1 V/SCE), thus affording an electrolytic zinc. 

The isoprenylation of isovaleraldehyde led to the product in 68% isolated yield, higher than with a conventional procedure using zinc dust in DMF, or refluxing THF. The same procedure was used for the coupling reaction of allylic bromides with aldehydes and ketones, via the preliminary formation of organozinc compounds coming from the reaction between the electrolytic zinc and allylic bromides12. 

The electrolytic zinc prepared in the presence of naphthalene at — 20 °C appears more reactive than that prepared in the absence of a mediator, as observed in equation 8. 

Under a high electrolysis current intensity, the zinc(II) ions electroformed in the active zinc vicinity prevent the chemical reaction from becoming the major process. In an undivided cell and under a high electrolysis current intensity, the anodic scoring of zinc is negligible. In this case, the organozinc compounds are produced after reaction of the electrolytic zinc with CF3Br (Scheme 7). 

The synthesis of organozinc compounds by electrochemical processes from either low reactive halogenated substrates (alkyl chlorides) or pseudo-halogenated substrates (phenol derivatives, mesylates, triflates etc.) remains an important challenge. Indeed, as mentioned above, the use of electrolytic zinc prepared from the reduction of a metal halide or from zinc(II) ions does not appear to be a convenient method. However, recent work reported by Tokuda and coworkers would suggest that the electroreduction of a zinc(II) species in the presence of naphthalene leads to the formation of a very active zinc capable of reacting even with low reactive substrates (equation 23)11. 

Notably, Zn2+ ions are more easily reduced than naphthalene. This indicates that the electroreduction of the latter is very likely achieved on a recovered electrolytic zinc cathode. What happens under these conditions So far, no data allow us to answer this question. The only information is the experimental observation of a characteristic transient color of the naphthalene anion radical indicating the reduction of this hydrocarbon, simultaneously with the reduction of Zn2+, owing likely to a too high current density set at the cathode11. Moreover, the presence of an alkyl halide under such conditions would lead to its reduction on the zinc deposit, and this reduction would occur more easily than the reduction of naphthalene according to complex processes (equation 25). 

Several attempts were made with higher concentrations in Arl (up to 0.1 M) but failed. The major part of zinc is deposited at the electrode surface. These results match well those described in the first part of this chapter (see Section ). Indeed, in DMF, it has been clearly shown that the electrolytic zinc reacts only with activated alkyl halides. 

Asarco tested components of sulfur concrete, both precast and poured in place, in corrosive environments of sulfuric acid. Favorable endurance of these samples led to a full-scale cooperative demonstration project. The project selected was the rehabilitation of an electrolytic zinc cellhouse basement floor of approximately 21,000 square feet. 

Corpus Christi Feb. 1978 Slabs, electrolytic zinc refinery floors. 

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